Structure and dynamics of water confined in nanoporous carbon
YZ He and K Nomura and RK Kalia and A Nakano and P Vashishta, PHYSICAL REVIEW MATERIALS, 2, 115605 (2018).
We study the structure and dynamics of water confined in a nanoporous graphitic carbon structure using molecular-dynamics (MD) simulations. The carbon structure is generated by a reactive MD simulation of oxidation of a silicon carbide nanoparticle. We embed water molecules in the nanopores and study structural and dynamical properties of nanoconfined water as a function of temperature. MD simulation results indicate the presence of high-density water (HDW) and low-density water. Radial distribution functions and spatial density functions indicate that the second solvation shell of the HDW is broken. We calculate the self-diffusion coefficient of confined water molecules as a function of temperature and find a significant decrease in the diffusion of water molecules around T = 190K. The cage correlation function c(t) of confined water molecules at T = 200K exhibits stretched exponential decay, c(t) = exp-(t/tau) beta, with beta = 0.43, which matches exactly with the theoretical prediction beta = 3/7. Furthermore, the self-intermediate scattering function at T = 200K indicates differences in small-scale and large-scale dynamics of water molecules.
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